Body fat analyzer with integral analog measurement electrodes

ABSTRACT

A body fat analyzer having integrated measurement electrodes is disclosed. The assembly comprises a substrate; at least two conductive-film electrodes formed from a conductive material integrated on said substrate and capable of contacting a body to be measured; and a measurement circuit electrically connected to said electrodes. There is further disclosed a water-resistant body fat analyzer that comprises a substrate having top and bottom surfaces and an edge therebetween; at least two electrodes in contact with the top surface of the substrate, and capable of contacting an object having a biometric electrical characteristic to be measured; and a body fat measurement circuit mounted below the substrate and electrically connected to the electrodes such that the top surface of the substrate remains intact, whereby water present thereon is prevented from reaching the circuit. The invention is further directed to methods of manufacturing the disclosed body fat analyzers.

FIELD OF THE INVENTION

[0001] The present invention relates generally to a biometric dataacquisition assembly, and more particularly to a body fat analyzerhaving measurement electrodes made from a conductive film integrated ona substrate. It further relates to a water-resistant body fat analyzerhaving electrodes mounted on its upper surface and connected tomeasurement circuits within the analyzer without requiring perforationsin its upper surface.

BACKGROUND

[0002] Percent body fat has long been recognized as a useful indicatorof a person's health. One technique that has been developed to measure aperson's percent body fat is the so-called “bioelectrical impedance”technique. According to this technique, a person's body fat is measuredby determining the impedance of the person's body to electrical signals,and calculating the percent body fat based upon the measured impedanceand other variables such as height, weight, age, and sex. Body impedanceis typically determined by supplying a constant current through at leasttwo electrodes that contact the body, thereby causing a voltage todevelop across the body. This voltage is measured either (1) via thesame electrodes through which current is supplied, or (2) via one ormore pairs of voltage-measuring electrodes. The body impedance is thenreadily calculated from the current and the measured voltage, and thepercent body fat is in turn calculated from the body impedance.

[0003] Although many body fat analyzers based on these techniques arecurrently available in the retail market, they tend to have bulkyelectrodes, to be susceptible to damage from water, and to be relativelyexpensive to manufacture. One example of such a body fat analyzer isdescribed in U.S. Pat. No. 5,611,351 and shown in FIG. 1. With referenceto FIG. 1, a user stands on four large metal electrodes 2,3, throughwhich current is supplied and the developed voltage measured. The user'sweight and height are also measured, by a weight scale within base 5 andheight scale 4,4A. The user's body impedance and body fat are thencalculated and displayed on display 6. A plan view of base 5 is shown inFIG. 2, and a sectional view is shown in FIG. 3. From these figures, itmay be seen that electrodes 2,3 are large, thick, and bulky. Suchelectrodes are relatively expensive to manufacture, since they require alarge amount of raw material and processing. Further from FIGS. 1-3,although the wiring associated with electrodes 2,3 is not directlyindicated, they appear to be connected to the measurement and displaycircuitry 6 via conductors that pass through openings in the uppersurface I of base 5. These openings may disadvantageously permit waterand dust to enter base 5. Moreover, despite the size of electrodes 2,3,the user is required, by their geometry and by heel guides 7, to placehis feet in very specific locations, which may not be comfortable forusers of different body types. Finally, since electrodes 2,3 alonesupport the user's weight, he may feel some discomfort as the electrodespress into his feet.

[0004] A more recent bioimpedance body fat analyzer, described in U.S.Pat. No. 6,308,096 and shown in FIGS. 4 and 5, comprises a handheld unit40 and a base unit 42, connected by a cord 44. The analyzer has eightelectrodes, four in handheld unit 40 and four in base unit 42. It may beseen from FIG. 5 that the base-mounted electrodes 50, 52 in this bodyfat analyzer are relatively small, and flush-mounted in a rubber support54, itself mounted on a base 56 and held in position by upper layer 58.Although this body fat analyzer is more comfortable to use than thatdescribed above, it is still relatively expensive to manufacture becauseof the large number of manufacturing steps required to mold electrodes50, 52, mount them in rubber support 54 and then install the assembly inposition between base 56 and upper layer 58.

[0005] Still another recent body fat analyzer is described in U.S. Pat.No. 6,243,651 and shown in FIGS. 6 and 7. This analyzer is lessexpensive to produce than those described above, since it is a small,handheld unit having a compact plastic case 60 and four small electrodes62. Electrodes 62 are made of stainless steel (SUS) sheet metal, whichcan be produced and installed more easily than the molded electrodes inthe analyzers described above. But this analyzer, too, requires manualassembly and thus is still relatively expensive to produce.Additionally, like the analyzers described above, this analyzer issusceptible to damage by moisture that may reach the inside of the unitthrough openings in the case 60 around the keys 64, display 66, or atthe points at which electrodes 62 (or their associated conductors) entercase 60.

SUMMARY OF INVENTION

[0006] It is therefore an object of the present invention to provide abody fat analyzer having a reduced risk of damage by environmentalfactors.

[0007] It is a still further object of the present invention to providea body fat analyzer that may be easily and inexpensively mass-produced.

[0008] The inventor of the present invention has accomplished theseobjectives through the application of conductive-film integrationtechnology to body fat analyzers. Thus, a body fat analyzer inaccordance with the invention preferably comprises a substrate; at leasttwo conductive-film electrodes integrated on the substrate and capableof contacting a body to be measured; and a body fat measurement circuitelectrically connected to the electrodes.

[0009] A problem that arises when such an analyzer is constructed isthat conductive-film electrodes have high resistances, e.g., between1-100 ohms, which affects the measured value of resistance. Inaccordance with the present invention, this problem is overcome byconfiguring the body fat measurement circuit to calculate, based uponthe measured body impedance, a corrected body impedance value that isindependent of the impedance of the electrodes.

[0010] The substrate may be composed of any non-conductive materialcapable of receiving a conductive-film layer. Suitable materialsinclude, e.g., glass, ceramics, plastics, non-conductive stones, andinsulators.

[0011] The electrodes may be composed of any conductive material suitedto application as a conductive film on a substrate, e.g., metals,semiconductors, conductive inks and pastes, and transparent conductivematerials such as zinc stannate (ZnSnO₃ and Zn₂SnO₄), fluorine-dopedzinc oxide (ZnO:F), indium tin oxide (In₂0:Sn and In₂O₃:Sn), titaniumnitride (TiN_(x)), and fluorine-doped tin oxide (SnO₂:F). In order tominimize material and processing costs while maintaining a suitableconductance, the electrodes are preferably between 20 nanometers to 5micrometers thick.

[0012] Preferably, a body fat analyzer in accordance with the inventionfurther comprises a heating element in contact with the substrate andcapable of warming the surface of the analyzer. This warming actionrenders the analyzer more comfortable to use and may also increase theaccuracy of the body fat measurement, since better capillary blood flowat the surface of the foot results. To control the heating element, acurrent source electrically connected to it is also required. Still morepreferably, since the conductive-film electrodes themselves have arelatively high resistance, they may be used as the heating elements,and the current source may be included in the body fat measurementcircuit.

[0013] In a further embodiment of the present invention, other circuitsuseful in body fat analyzers may be additionally provided on thesubstrate as integrated circuits. Such circuits may include, forexample, a thin-panel display, a touch-switch keypad, and anelectromagnetic shield positioned to protect the measurement circuit.Preferably, the measurement circuit itself is integrated on or under thesubstrate.

[0014] The present invention further includes a method of producing abody fat analyzer, comprising the steps of: (1) forming two or moreconductive-film electrodes on a substrate; and (2) electricallyconnecting a biometric data acquisition circuit to the electrodes. Theelectrodes may be formed on the substrate by known thin- or thick-filmintegration techniques, such as sputtering, vapor deposition,photolithography, screen-printing, etc. The electrodes may be shaped byeither of two known techniques: (1) creating a uniform layer ofconductive material on the substrate; and selectively removingpredetermined portions of the conductive material by, e.g., chemicallyetching, sand-blasting, laser patterning, or grinding away predeterminedportions of the conductive material; or (2) by applying the electrodematerial only to selected portions of the substrate. Preferably, themethod of producing the body fat analyzer further comprises the step ofadditionally integrating, on the substrate, at least one of (1) athin-panel display, (2) a touch-switch keypad, (3) a heater element, and(4) an electromagnetic shield.

[0015] In another embodiment of the invention, a body fat analyzerhaving improved water-resistance is provided. It comprises a substratehaving top and bottom surfaces and an edge therebetween; at least twoelectrodes in contact with the top surface of the substrate, and capableof contacting an object having a biometric electrical characteristic tobe measured; and a body fat measurement circuit mounted below thesubstrate and electrically connected to the electrodes such that the topsurface of the substrate remains intact, whereby water present thereonis prevented from reaching the circuit. Preferably, the circuit islocated below the bottom surface of the substrate and is connected toeach of the electrodes via a conductive path traversing the edge of thesubstrate. To further improve the water-resistance of the analyzer, agasket is preferably mounted on the substrate that tends to keep waterpresent on the top surface of the substrate from reaching the bottomsurface of the substrate.

[0016] The invention, in this embodiment, further includes a method ofproducing a body fat analyzer, comprising the steps of: (1) affixing atleast two electrodes on the top surface of a substrate having top andbottom surfaces and an edge therebetween; and (2) electricallyconnecting the electrodes to a biometric data acquisition circuitmounted below the substrate, such that the top surface of the substrateremains intact, whereby water present thereon is prevented from reachingthe circuit. Preferably, the connecting step includes the step ofproviding, for each electrode, a conductive path from the electrode onthe substrate's top surface to its bottom surface via its edge. Finally,the method preferably includes the step of providing, near the edge ofthe substrate, a gasket that tends to keep water present on the topsurface of the substrate from reaching the bottom surface of thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A fuller understanding of the present invention may be obtainedby reference to the following detailed description and to the drawings,wherein like reference numerals are used to identify similar componentsin the various figures and in which:

[0018]FIGS. 1-3 depict various views of a prior art body fat analyzer.

[0019]FIGS. 4-5 depict plan and sectional views of another prior artbody fat analyzer.

[0020]FIGS. 6-7 depict plan and sectional views of yet another prior artbody fat analyzer.

[0021]FIGS. 8-9 depict body fat analyzers in accordance with oneembodiment of the present invention; and

[0022]FIG. 10 depicts a body fat analyzer in accordance with anotherembodiment of the present invention.

DETAILED DESCRIPTION

[0023]FIG. 8 illustrates a body fat analyzer in accordance with oneembodiment of the present invention. It comprises substrate 86, two ormore measurement electrodes 80-83, display unit 84, a measurementcircuit (not shown) located within display unit 84, and weight sensors87-90.

[0024] Suitable measurement circuits for use inbioelectrical-impedance-based body fat analyzers are well-known, anddescribed, e.g., in the prior art references discussed above.

[0025] Substrate 86 may be composed of any non-conductive materialcapable of receiving a conductive-film layer. Suitable materialsinclude, e.g., glass, ceramics, plastics, non-conductive stones, andinsulators. Hardened glass, however, is a preferred material, because ofits strength, rigidity, and aesthetic qualities.

[0026] Electrodes 80-83 may be composed of any conductive materialsuitable for application as a conductive film on the substrate, usingeither thin-film or thick-film technology. A variety of metals,semiconductors, conductive inks and pastes, and TCMs such as zincstannate (ZnSnO₃ and Zn₂SnO₄), fluorine-doped zinc oxide (ZnO:F), indiumtin oxide (In₂0:Sn and In₂O₃:Sn), titanium nitride (TiN_(x)), andfluorine-doped tin oxide (SnO₂:F) have been successfully used to formconductive films in the manufacture of integrated circuits, thin-paneldisplays (including both liquid crystal displays and thin-filmelectroluminescent (“TFEL”) displays), touch screens, and automobileglass, and are suitable for use with the present invention. TCMs arepreferred materials for the electrodes, since their color andtransparency can be controlled by the selection of the material or theaddition of an ink to the material. It is thereby possible to produce acolored pattern on the substrate that can be very attractive. One suchpattern is shown in FIG. 8; another is shown in FIG. 9.

[0027] The specific electrode material selected, however, will depend onprocess and customer requirements. Among the TCMs, for example, ZnO:Fand Cd₂SnO₄ have the highest transparency. In₂O:Sn has the highestconductivity. TiN and SnO₂:F have a high mechanical durability. SnO₂:Fhas the best chemical durability. ZnO:F and TiN are the easiest to etch.Overall, In₂O₃:Sn has the highest conductivity, better transparency andeasier etchability, and is therefore favored over other TCMs for use inpatterning artwork electrodes for body fat analyzer applications.

[0028] The conductive-film electrodes may be produced on the substrateby known thin-and thick-film integration techniques, including adhesion,vapor deposition, cathodic arc deposition, sputtering, photolithography,spin-coating, and screen-printing. These techniques are well-known inthe art. See, e.g., U.S. Pat. Nos. 6,315,874; 6,312,837; 5,122,391; and6,146,765; and P. K. Vasudev, Integrated Circuit Fabrication, inELECTRONIC ENGINEERING HANDBOOK 11.1 (Donald Christiansen et al. eds.,4th ed. 1997).

[0029] Two general methods of shaping the electrodes are available: (1)applying the electrode material uniformly onto the substrate, and thenselectively removing it from selected areas of the substrate glassplatform via sand-blasting, etching, laser patterning, grinding, etc.;or (2) by applying the electrode material only to selected portions ofthe substrate, as, for example, by (a) applying a mask layer beforeapplying the conductive material to the substrate, and then removing themask layer, or (b) screen-printing the conductive material through apatterned screen.

[0030] The thickness that is appropriate for the conductive-filmelectrodes is based on the stoichiometry of the substrate and theconductive-film material, the stresses placed on the material in themanufacturing process, the desired manufacturing time, the desiredelectrode resistance, and, in the case of transparent conductivematerials, the desired transparency. Existing conductive-film conductorsare typically between 20 nanometers to 5 micrometers thick. A thickelectrode tends to be stronger and more resistant to stresses, havelower resistance, require a longer manufacturing time, and (in the caseof a TCM) be less transparent. For example, a 100 ohm TCM coating willbe approximately 20 nm thick, whereas a 10 ohm coating will beapproximately 200 nm thick. Similarly, a 20 nm TCM layer will havetransmittance around 90% and etching time less than 90 seconds, whereasa 200 nm thickness will have transmittance around 85% and etching timearound 300 seconds. However, for body fat analyzers, the transmittanceand etching time are less important than the electrode resistance. In apreferred embodiment, which has been reduced to practice, a TCM coating(of indium-tin-oxide) of 180 nm thickness was used, resulting in anelectrode resistance of about 10 ohms but a transmittance of only about85%.

[0031] Even this electrode resistance of 10 ohms can be very high incomparison with a typical body impedance, however, which can be as lowas about 100 ohms. Accordingly, in the present invention, it ispreferable to configure the measurement circuit such that it correctsfor the electrode impedance, e.g., by comparing the impedance measuredacross the body with that measured across internal calibrationimpedances. By means of such a technique, which is now well-known in thebody fat measurement art and described, e.g., in U.S. Pat. No.5,611,351, a corrected body impedance value may be obtained that isindependent of the impedance of the electrodes.

[0032] Preferably, the body fat analyzer in accordance with theinvention further comprises a heating element in contact with thesubstrate and capable of warming the surface of the analyzer. Thiswarming action renders the analyzer more comfortable to use and mayincrease the accuracy of the body fat measurement, since bettercapillary blood flow at the surface of the foot results. To control theheating element, a current source electrically connected to it is alsorequired. Still more preferably, since the conductive-film electrodesthemselves have a relatively high resistance, they may be used as theheating elements, and the current source may be included in the body fatmeasurement circuit.

[0033] In a further embodiment of the present invention, other circuitryused in body fat analyzers may be additionally provided on the substrateas integrated circuits. Such circuits may include, for example, athin-panel display, a touch-switch keypad, and an electromagnetic shieldpositioned to protect the measurement circuit. Preferably, themeasurement circuit itself is also integrated on the substrate.

[0034] Connections from the measurement circuit to the conductive-filmelectrodes may be made either via integrated conductive traces (as inFIGS. 8 and 9), or via wire conductors, as shown in FIG. 10. If thelatter method is used, solder pads 110-113 may be provided that permitthe conductors 131-134 to be easily soldered to the conductive-filmelectrodes. Such pads can be manufactured, e.g., by screen-printingsolder paste at the desired locations and then heat-treating the pasteat a temperature sufficient to allow it to dry or cure.

[0035] Solder pads 110-113 may be provided either (1) on the uppersurface of electrodes 100-103 or (2) on the lower surface of substrate150. If they are mounted on electrodes 100-103, conductors 131-134 arepreferably routed from the measurement circuit below substrate 150 uparound its edges to solder pads 110-1 13, respectively, without passingthrough perforations in the surface of substrate 150. If they aremounted on the lower surface of substrate 150, however, conductivetraces must be provided from electrodes 100-103 to solder pads 110-113.These traces are preferably formed from the same material as thatforming electrodes 100-103 and routed, as described above, around theedge of substrate 150 to the solder pads below. In this way, connectionsfrom the measurement circuit to the electrodes may be made withoutrequiring holes or penetrations in substrate 150. It will be recognizedthat the resulting body fat analyzer will have enhanced water-resistantcharacteristics over existing body fat analyzers.

[0036] To further improve the water-resistance of the analyzer, a gasketmay preferably be mounted around the edge of the substrate, which tendsto keep water present on the top surface of the substrate from reachingits bottom surface. Suitably-shaped gaskets are commercially availableand will not be further described herein.

[0037] The invention thus further includes a method of producing a bodyfat analyzer, comprising the steps of: (1) affixing at least twoelectrodes on the top surface of a substrate having top and bottomsurfaces and an edge therebetween; and (2) electrically connecting tothe electrodes a body fat measurement circuit mounted below thesubstrate, such that the top surface of the substrate remains intact,whereby water present thereon is prevented from reaching the circuit.Preferably, the connecting step includes the step of providing, for eachelectrode, a conductive path (e.g., a wire conductor or a conductivetrace) from the substrate's top surface to its bottom surface via itsedge. Finally, the method preferably includes the step of providing,near the edge of the substrate, a gasket that tends to keep waterpresent on the top surface of the substrate from reaching the bottomsurface of the substrate.

[0038] In summary, there has been disclosed a body fat analyzer havingconductive-film electrodes that are integrated onto the surface of asuitable substrate, such as glass. A body fat analyzers produced inaccordance with the invention has a number of advantages over existingbody fat scales, including improved resistance to environmentalpollutants, a reduced cost to manufacture, and an electrode pattern thatpermits a wide range of standing positions for the user.

[0039] It should be understood that the embodiments described herein aremerely illustrative and not intended to limit the scope of theinvention. For example, it will be recognized that the present inventionis not limited only to body fat analyzers but is rather applicable toany biometric data acquisition device, as reflected in the claims below.Additionally, one skilled in the art may make various changes,rearrangements and modifications without substantially departing fromthe principles of the invention, which is limited only in accordancewith the claims.

1-11. Cancelled.
 12. A method of producing a biometric data acquisitionassembly, comprising the steps of: a. forming two or moreconductive-film electrodes on a substrate, each having an impedance; b.electrically connecting a biometric data acquisition circuit to theelectrodes; c. forming at least one reference conductive film electrode;and d. electrically connecting the biometric data acquisition circuit tothe reference electrode to correct for the conductive-film electrodeimpedance.
 13. The method of claim 12, wherein the two or moreelectrodes are formed by one of adhesion, vapor deposition, cathodic arcdeposition, sputtering, photolithography, spin-coating, andscreen-printing.
 14. The method of claim 12, wherein said step offorming comprises the steps of: a. creating a uniform layer ofconductive material on the substrate; and b. selectively removingpredetermined portions of the conductive material, such that the two ormore electrodes are produced.
 15. The method of claim 14, wherein saidremoving step is performed by one of chemically etching, sand-blasting,laser patterning, and grinding predetermined portions of the conductivematerial.
 16. The method of claim 12, wherein said step of formingcomprises the step of: a. applying a mask layer to portions of thesubstrate; b. applying conductive material to the portions of thesubstrate not covered by the mask layer; and c. removing the mask layer.17. The method of claim 12, further comprising the step of additionallyintegrating, on the substrate, at least one of: a. a thin-panel display,b. a touch-switch keypad, c. a heater element, and d. an electromagneticshield. 18-20. Cancelled.
 21. A method of producing a biometric dataacquisition assembly, comprising the steps of: a. affixing at least twoelectrodes on the top surface of a substrate having top and bottomsurfaces and an edge therebetween; and b. electrically connecting to theelectrodes a biometric data acquisition circuit mounted below thesubstrate, while leaving the top surface of the substrate intact,whereby water present thereon is prevented from reaching the circuit.22. The method of claim 21, wherein said step of connecting comprisesthe step of providing, for each electrode, a conductive path from thesubstrate's top surface to its bottom surface via its edge.
 23. Themethod of claim 22, further comprising the step of providing, near theedge of the substrate, a gasket that tends to keep water present on thetop surface of said substrate from reaching the bottom surface of saidsubstrate.
 24. The method of claim 12, wherein the reference electrodeis an internal calibration impedance.